Germanium and silicon substituted manganese activated magnesium gallate phosphor

ABSTRACT

A method for manufacturing a phosphor material represented by the following general formula: yMgO2.(1 - x)Ga2O3.xMO2.pMnO where: MO2 an oxide selected from the group consisting of GeO2 and SiO2 0&lt;X &lt; OR = 0.3 0.70 &lt; OR = y &lt; OR = 1.05 0.001 &lt; OR = P &lt; OR = 0.05 WHICH COMPRISES SUBJECTING A MIXTURE OF OXIDES HAVING A COMPOSITION EXPRESSED BY THE GENERAL FORMULA TO A PRIMARY FIRING AT A TEMPERATURE OF FROM 1,100* TO 1,475* C. in an oxidizing atmosphere, grinding and mixing the fired mass, and subjecting the resultant mixture to a secondary firing at a temperature of from 1,000* to 1,250* C. in a reducing atmosphere.

United States Patent Inoue et al.

[451 June 20, 1972 [54] GERMANIUM AND SILICON SUBSTITUTED MANGANESEACTIVATED MAGNESIUM GALLATE PHOSPHOR [72] Inventors: Taiichi Inoue;Toshimasa Ueda, both of Tokyo, Japan [73] Assignee: Tokyo ShibauraElectric Co., Ltd.,

Kawasaki-shi, Japan [22] Filed: May 4, 1970 [21] Appl.No.: 34,322

[30] Foreign Application Priority Data May 8, 1969 Japan ..44/35067 May10, 1969 Japan ..44/35643 [52] US. Cl ..252/30L4 F [51] Int. Cl. ...C09k1/04,C09k 1/54 [58] Field ofSearch. ..252/30l.4 R, 301.4F

[56] References Cited UNITED STATES PATENTS 3,576,757 4/1971 Brown, Jr..252/301.4 R

3,407,325 10/1968 Brown, Jr ..252/30l.4 R 3,499,843 3/1970 Brown, Jr. etal.. ..252/30L4 R FOREIGN PATENTS OR APPLICATIONS 465,210 5/1950 Canada..252/30L4 R Primary Examiner-Robert D. Edmonds Attorneyl(emon, Palmer &Estabrook [57] ABSTRACT A method for manufacturing a phosphor materialrepresented by the following general formula:

where:

M0: an oxide selected from the group consisting of GeO and SiO 3 Claims,8 Drawing Figures rmmmmzo I972 3,671 A52 sum 1 or 4 FIG. 1

GeOz- SUBSTITUTED mol NUMBER x FIG. 2

IOO

80- 0.95MgO-(1-x)Ga 0 -xGe0 -O.O1MnO Ge 0 SUBSTITUTED mol NUIVBER x v IN VE A TOR.

RELATIVE SPECTRAL ENERGY PKTE'N'TEDJum I972 saw 2 or 4 FIG.

0:2 6.3 SiOg SUBSTITUTED mol NUMBER x FIG.

0.5 NLMBER x 0.1 SiOg SUBSTITUTED mOl I N VE N TOR.

P'ATENTEnJunzo I972 SHEET 3 N 4 ao 'aosmo v F I G. 5 bssm o-oasso o -ameOSSMQO'GOQSQ-QW wAvE LENGTH (nun-- Fl G. J a

IN V NTOR.

PATENTEnaunzo I972 RELATIVE SPECTRAL ENERGY (OPTIONAL) lx auholmqm SHEEI0F 4 FIG. 6

WAVE- LENGTH (nm) INVENTOR.

GERMANIUM AND SILICON SUBSTITUTED MANGANESE ACTIVATED MAGNESIUM GALLATEPI'IOSPI'IOR The present invention relates to a method for producingphosphor material emitting a blue-green light. A fluorescent lamp usedin electronic photography, for example, xerography is generally requiredto emit a blue-green light. A phosphor material giving forth such ablue-green light has heretofore consisted of manganese-activatedmagnesium-gallium oxides l0 (Mg,Ga,OB3/Mn,,; y 0.001 to 0.05, x y 0.75to 1.05). (Refer to the US. Pat. No. 3,407,325, British Patent 1,105,233or West Germany Patent 1,246,914). However, this phosphor material hadan insufficient efficiency and a prior art fluorescent lamp forxerography using said phosphor material only gave a low output. This ledto the drawbacks that the xerography formerly required a long time ofexposure, failing to prepare a large number of xerographic copies perunit time.

A phosphor material obtained by the method of the present inventioncomprises manganese-activated magnesium-gallium oxides, part of which issubstituted by germanium dioxide or silicon dioxide as indicated by thefollowing general formula (1):

M0 an oxide selected from the group consisting of Ge0 and Si0 0.001 s ps 0.05

The phosphor material can be prepared by first subjecting raw powderscorresponding to the composition represented by the formula I to aprimary firing in an oxidizing atmosphere, followed by grinding andmixing and then subjecting the resultant mixed powders to a secondaryfiring in a reducing atmosphere. Through Mn involved in the rawcomposition becomes tetravalent during the primary firing, it is reducedto a divalent state by the secondary firing. As a result, Mn0 firmlyretains said divalent state and serves as an activator for the hostmaterial, consisting of yMg0-( l Ga 0 -xM0 I An object of the presentinvention is to provide a method for manufacturing a phosphor materialgiving forth a bluegreen light which more effectively emits suchfluorescence than the prior art type consisting of manganese-activatedmagnesium-gallium oxide. Another object is to offer a blue-green lightemitting phosphor material which generates a greater energy output thanthe conventional type. Still another object is to provide a phosphormaterial for xerography which only requires a relatively shorter time ofexposure and enables a larger number of xerographic copies to be formedper unit time than has been realized in the past. A further object to tomanufacture such phosphor material displaying a high fluorescentefficiency at relatively low cost.

The further objects and advantages of the present invention will be moreapparent from the following description taken by reference to theappended drawings, in which:

FIG. I is a curve diagram showing the shifts of the peak wave length inthe spectral energy distributions of phosphor materials according to aseries of examples of the present invention, and including some dataoutside the scope of the invention, in proportion to increases in thegermanium-substituted mol number x,-

FIG. 2 is a curve diagram showing variations in the relative intensityof the spectral energy of the phosphor material according to increasesin the value of x in FIG. 1;

FIG. 3 is a curve diagram showing the shifts of the peak wave lengths inthe spectral energy distributions of a phosphor materials according toanother series of examples of the invention, and including some dataoutside the scope of the invention, in proportion to increases in thesilicon-substituted mol numberx;

FIG. 4 is a curve diagram showing changes in the relative intensity ofthe spectral energy of the phosphor material of FIG. 3 according tovariations in the value of .r;

FIG. 5 is a curve diagram comparing the spectral energy distribution ofthe prior art phosphor material with that of a phosphor materialaccording to still another example of the invention wherein the galliumis substituted by germanium dioxide;

FIG. 6'is a curve diagram comparing the spectral energy distribution ofa phosphor material wherein the gallium is partly substituted by silicondioxide according to a further example of the invention, with that ofthe prior art type;

FIG. 7 is a front elevation of a fluorescent lamp using the phosphormaterial of the invention adapted for xerography; and

FIG. 8 is a cross sectional view of the same.

There will now be described by reference to FIGS. 1 to 4 therelationship between the proportions of the components constituting thephosphor material of the present invention and its light-emittingproperties. FIG. 1 relates to a phosphor material wherein the term M0,of the aforementioned formula 1 consists of Ge0 and shows variations inthe peak wave length of the spectral energy of said material, where y isfixed at 0.95, p'

at 0.01 and x denotes a variable. As apparent from this figure, when themol number .r of gallium substituted by germanium increases, then thepeak wave length is gradually shifted toward the long wave side.However, where x ranges between 0 and 0.3, then said shift only amountsto about 5.5 nm, presenting no practical difficulties. And the peak wavelength lies between 501 nm and 506.5 nm, enabling the emission of a goodblue-green light. FIG. 2 shows variations in the relative intensity ofthe spectral energy of FIG. I, where the spectral energy of the priorart phosphor material (x =0) is taken as and x is considered as avariant. As seen from this figure, in case of 0 .r 0.3, the phosphormaterial of the present invention gives a larger output than theconventional type. Particularly where .r lies' between 0.1 and 0.2, thepresent phosphor material generates a prominently greater or about 20percent larger energy output. There have been described the propertiesof a phosphor material according to the present invention where y and pamount to 0.95 and 0.01 respectively. Still in case of0.98 y a 0.92 and0.02 B p 2 0.005, said properties do not substantially vary. Further incase of l .05 a y z 0.98, 0.92 2 y a 0.70 and 0.05 I p i 0.02,0.005 p .z0.00], said properties even display a better effect than has beenpossible in the past, though they decrease from those associated withthe aforementioned optimum range. If however, y lies outside of therange between 0.70 and 1.05 and p departs from the limit of 0.001 to0.05, then the phosphor material of the present invention varies littlefrom the prior art product in effect. Particularly when p exceeds 0.05,the phosphor material bears a foreign color harmfully affecting itsproperties.

FIG. 3 represents variations in the peak wave length (nm) of thespectral energy of the phosphor material of the present invention, whereM0 of the aforementioned equation 1 is represented by Si0 y is fixed at0.95, p at 0.01 and x is varied. As apparent from this figure, when thegallium is substituted by silicon in increasing mol members, a peak wavelength in the spectral energy distribution is gradually shifted towardthe long wave side. However, where the value of .r ranges between 0 and0.3, said shift only amounts to 6.0 nm, presenting no practicaldifficulties but permitting the emission of a good blue-green light.FIG. 4 indicates variations in the relative intensity of the spectralenergy of the phosphor material of FIG. 3, where the spectral energy ofthe prior art phosphor material is taken as 100 and x is considered as avariant. The figure shows that in case of 0 x a 0.3, the phosphormaterial of the present invention generates a larger output than theconventional product, and particularly in case .r lies between 0.05 and0.1, said output increases about 15 percent over the level which hasbeen possible in the past. There have been described the properties of aphosphor material according to the present invention, where y denotes0.95 and p 0.01. Still in case of0.98 y i 0.92 and 0.02 a p 2 0.005,said properties vary little. Furtherin case of 1.05 z y a 0.98, 0.92 B yi 0.70 and 0.05 B p Z 0.02, 0.005 a p a 0.001, the

properties even display a better effect than has been realized in thepast, though they decrease from those associated with the aforesaidoptimum range. If, however, y lies outside of the range between 0.70 and1.05 and p departs from the limit of phosphor materials. (The secondaryfiring of all samples Nos. 1 to 20 may be conducted at temperatures ofl,000 to 1,250" C.) The reducing atmosphere consisted of a mixture of lpercent by volume of hydrogen and 99 percent by volume of 0.001 to 0.05,then the phosphor material of the present innitrogen. vention varieslittle from the prior art product in effect. Par- FIG. 2 represents therelative intensity of the spectral enerticularly when y falls from 0.70,the phosphor material gy of samples Nos. 1 to excited by ultravioletrays of 253.7 decreases in resistance to heating in the air, so that itsnm with that of the prior art product taken as 100. Further. fluorescentefficiency is undesirably reduced when the materidetermination was madeof the spectral energy distribution of al is fired during the process ofmanufacturing a fluorescent 10 samples Nos. 1 to 10 when they wereexcited similarly by ullamp. Further, when p exceeds 0.05, the phosphormaterial ittraviolet rays of 253.7 nm. FIG. 5 indicates the spectralenergy self bears a foreign color harmfully affecting its properties. Iti ri i n o mpl No- I (used as r n n 5 will be noted that the a e whereart of the allium oxide i which were considered as typical specimens. Asseen from substituted by both Ge0 and SiO,, it is still deemed amodifica- FIG. 5, a phosphor material according to the present inventiontion of the present invention. emits a spectral energy approximatelypercent larger than The present invention will be more clearlyunderstood from the prior art product, and the emission peak of thelatter has the following example. There were prepared samples of a thealmost same wave length as that of the former (thereby phosphor materialconsisting of manganese-activated oxides emitting blue-green g ofmagnesium, gallium and germanium expressed by a chemi- Where there isgenerally manufactured a fluorescent lamp, cal formula yMgO-(l -.\')Ga 0xGeO -Mn0 where y is fixed 20 the inside wall surface of the glass bulbis coated with a at 0.95 and p at 0.01 and .r is varied as listed inTable 1 below. p p material, and firing is conducted at a temperature ofThere was further prepared another set of samples consisting 550 C. toexpel the organic binder contained in said material. ofmanganese-activated oxides of magnesium, gallium and sil- At thIS time,the gh n f h phosphor material slightly icon expressed by a chemical f l0- 1 0 falls. To study the extent of said fall, there was conducted Si0-Mn0 where is fixed at 0.95 and p at 0.01 and x is varied another testIn which 5 g f each sample of a p p materias given in Table 2 below. Itwill be noted that samples Nos. 1 a] was Placed a till-lartz dish.followed y h i g m l and 1 1 are induded i T l 1 and 2 respectivdy as inthe air at a temperature of 550 C. The test shows that as apreferentialsamples representing the same type as the prior art P from tabie 3below, the brightnes decreases f [he phosphor "13181131 and 9 1Q, 19 and20 denote 30 phosphor materials of the present invention are practicallyreferential samples outside of the scope of the present inven-. equal tothat of the P an Product consldenng the p tion wherein x is greater than0.3 mol. mental error- TABLE 1 Proportions mixed Primary firingSecondary firing Sample MgO (15.03 (30.02 M11003 Temp. Time Temp. Timenumber X (g.) (g.) (g-) (g) C-) 0 TABLE 2 Proportions mixed Primaryfiring Secondary firing GazOa SiOz M11003 Tem Time Tem Time (8) (g) (3-)G- (11.) C. (11.

Samples Nos. 1 to 20 were prepared by weighing out the TABLE3 sufiicientamounts of raw powdered mater als to produce Samples of phosphormaterial X Rate of decrease (e76) component oxides having theproportlons indicated in Tables 1 22 1 and 2, followed by full mixing.Each mixture was placed in a 3 21 50 cc uncovered quartz crucible andsubjected to a primary g2; 8:2 38 firing in the air. The primary firingwas carried out with time 6 Q20 24 and temperature varied according tothe value of .1, namely, as No. 8 0.30 21 shown in Tables '1 and 2. Thefired mixture was gently ground FIG. 4 represents the relative intensityof the spectral enerin a mortar, and sieved by a 270-mesh nylon screen.The mass gy of samples Nos. 11 to 20 excited by ultra-violet rays of wasagain received in a 50 cc uncovered quartz crucible, fired 253.7 nm withthe spectral energy of the prior art product 1 hour in a reducingatmosphere by heating to l,l50 to taken as 100. Further, determinationwas made of the spectral l,250 C. for samples Nos. 1 to ID and l,000 tol,l50 C. for energy distribution of said samples similarly excited byulsamples Nos. 1 l to 20, and thereafier cooled to room temtravioletrays. FIG. 6 shows the spectral energy distributions of perature in thesame atmosphere, obtaining a variety of samples No. l l (x 0, used asreference) and No. 14 which were considered as typical specimens. Asapparent from FIG. 6, a phosphor material according to the presentinvention emits an approximately percent larger spectral energy than theprior art product, and the emission peak of the latter has the almostsame wave length as that of the former (thereby emitting blue-greenlight).

Where there is generally manufactured a fluorescent lamp, the inner wallsurface of the glass envelope is coated with a phosphor material, andfiring is conducted at a temperature of 550 C. to expel the organicbinder contained in said material. At this time. the brightness of thephosphor material slightly falls. To study the extent of said fall,there was carried out another test in which there was placed 5 g of eachsample of a phosphor material in a quartz dish, followed by heating 30minutes in the air at a temperature of 550 C. The test shows that asseen from table 4 below, the brightness decreases of the phosphormaterials of the present invention are smaller by 4 to 7 percent thanthat of the conventional product.

TABLE 4 Samples of phosphor material X Rate of decrease No. 11 0 22 No.12 0.01 18 No. 13 0.05 17 No. 14 0.1 17 No. 15 0.15 18 No. 16 0.20 16No. 17 0.25 16 No. 18 0.30 15 No. 19 0.40 15 No. 20 0.50 14 There willnow be described by reference to FIGS. 7 and 8 a fluorescent lamp forxerography applying a phosphor material according to the presentinvention. A cylindrical glass en-' velope 1 being open at both ends andhaving 485 mm length and 24 mm in outside diameter is provided. Theinside wall surface of the envelope 1 is coated with a suspensionprepared by suspending titanium dioxide in a solution of nitrocellulosein butyl acetate. After drying, the coating is fired about 5 minutes ata temperature of about 550 C. to form a reflection layer 2 onlyconsisting of titanium dioxide. The reflection layer is scraped off 8 mmwidth along the longitudinal direction of the envelope 1 to form anarrow-transparent region or window 3. The reflection layer 2 is againcoated with a suspension prepared by suspending a phosphor materialaccording to the present invention in a solution of nitrocellulose inbutyl acetate. After drying the coating, firing is conducted about 5minutes at a temperature of 550 C. to form a a fluorescent layer 4. lnthis case, the phosphor material deposited on the narrow-transparentregion 3 is fully removed as shown in FIG. 8. The subsequent steps areperformed in the same method as used in manufacturing a generalfluorescent lamp. Thus, electrodes 5 are fixed at the inside of bothends of the envelope 1, followed by evacuation; a small amount ofmercury and argon gas are put into the envelope 1; the envelope l issealed; and then finally bases 6 are fixed at the outside of both endsof the envelope 1, obtaining a 30-watt florescent lamp.

Type of fluorescent lamp Relative output According to the presentinvention 240 (containing Geo According to the present invention(containing Si0,) According to the prior art 200 As seen from the abovedata, the relative light outputs of fluorescent lamps applying aphosphor material according to the present invention are about 20percent greater than the conventional type. On the lamp applied thephosphor material containing germanium dioxide, the improved output isattributed to 20 percent output increase of the phosphor materia1itself. In silicon dioxide, it is attributed to both 15 percent outputincrease by reduction of the output deterioration which unavoidablyoccurs in the manufacture of a fluorescent lamp.

The foregoing example relates to the case where a phosphor materialaccording to the present invention was used in a fluorescent lamp forxerography. it will be apparent, however, that the phosphor material ofthe present invention is not limited to such use, but is applicable toother fluorescent lamps giving forth a blue-green light, for example,those for ornamental purposes or to a general fluorescent lamp forlighting purposes as an additional green light component by beingincorporated with other phosphor materials.

As mentioned above, the phosphor material of the present inventionexhibits a larger energy output than the same type of the prior artsubstantially without changing the color of a generated light andelevates the output of the resultant fluorescent lamp to an extent ofabout 20 percent and has the additional advantage that partialsubstitution of extremely ex pensive gallium (Ga) by germanium (Ge) orsilicon (Si) enables said phosphor material to be manufactured at lowcost.

What we claim is:

l. A blue-green light emitting magnesium gallate phosphor material ofthe formula:

yMg0-( l.\')Ga 0 'xM0 'pMn0 where:

M0 is an oxide selected from the group consist of Ge0 and 0.70 5 y 5[.05 and 2. A phosphor material of claim 1 wherein y lies between 0.92and 0.98 and p lies between 0.02 and 0.005.

3. A phosphor material of claim 2 wherein y 0.01.

0.95 and p

2. A phosphor material of claim 1 wherein y lies between 0.92 and 0.98 and p lies between 0.02 and 0.005.
 3. A phosphor material of claim 2 wherein y 0.95 and p 0.01. 